Deciphering the transformation mechanism of substituted polycyclic aromatic hydrocarbons on Al(III)-montmorillonite: An experimental and density functional theory study

Jinsong Liu; Chi Zhang; Song Zhao; Kecheng Zhu; Jinbo Liu; Zhiqiang Wang; Yunchao Dai; Hanzhong Jia

doi:10.1016/j.scitotenv.2021.147493

Deciphering the transformation mechanism of substituted polycyclic aromatic hydrocarbons on Al(III)-montmorillonite: An experimental and density functional theory study

Sci Total Environ. 2021 Sep 10:786:147493. doi: 10.1016/j.scitotenv.2021.147493. Epub 2021 May 3.

Authors

Jinsong Liu¹, Chi Zhang², Song Zhao¹, Kecheng Zhu¹, Jinbo Liu¹, Zhiqiang Wang¹, Yunchao Dai², Hanzhong Jia³

Affiliations

¹ College of Resources and Environment, Northwest A & F University, Yangling 712100, China.
² College of Resources and Environment, Northwest A & F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China.
³ College of Resources and Environment, Northwest A & F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China; State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Northwest A&F University, Yangling 712100, China. Electronic address: jiahz@nwafu.edu.cn.

PMID: 33984697
DOI: 10.1016/j.scitotenv.2021.147493

Abstract

The researches on transformation of polycyclic aromatic hydrocarbons (PAHs) on clay minerals modified by metal ions have received increasing attention. However, the transformation of PAHs with electron-withdrawing or electron-donating substitutional groups on clay minerals is not well understood currently. In this study, the degradation of anthracene (ANT) with different substituents (including -CH₃, -CHO, -Br, -OMe, and -NO₂) on Al(III)-montmorillonite (MMT) was investigated in the dark. The results showed that aromatic compounds were degraded with the rate constants (k_obs) of 0.004-0.141 d^-1. Moreover, ANT with electron-donating substituents (e.g., -CH₃, -OMe) had a higher transformation rate than that with electron-withdrawing substituents (e.g., -Br, -NO₂). The reactive oxygen species (ROS) quenching experiments indicated that ROS played a significant role in the transformation of ANT and ANT derivatives. Density functional theory (DFT) calculations revealed that the reactivity of single substituted PAHs was highly correlated with their ionization potential (IP), the energy of highest occupied molecular orbital (E_HOMO), the energy of lowest unoccupied molecular orbital (E_LUMO), and electronegativity (ζ), while independent of hardness (η). This study provides novel insights into predicting the reactivity of PAHs derivatives, and lays a fundamental basis for better understanding the fate of substituted PAHs in soils.

Keywords: ANT; Al(III)-montmorillonite; DFT calculations; Reactive oxygen species; Substituted PAHs.